There are known prior art constructions of orthopedic seat and backrest devices intended to improve seating posture and eliminate low back pain discomfort. Generally, these are characterized by seat and backrest portions which are rigidly connected together by a hinge or joint, whereat the innermost point of the seating space is defined. These devices are adapted for placement on the seat of a chair and against the back portion thereof, and because of their special contour, they provide a correction for poorly developed seating postures.
Examples of orthopedic seat design include those directed to the backrest portion along, as described in U.S. Pat. Nos. 4,601,514, to Meiller and 4,597,386 to Goldstein. Examples of designs featuring a hinged or jointed seat or backrest are described in U.S Pat. Nos. 4,696,516 to Yeum, 4,161,337 to Ross, et. al., 3,813,148 to Kraus and 3,778,104 to Kusters.
As stated previously, the intention of orthopedic seat design is to provide correct and comfortable seating posture and eliminate low back pain discomfort. The degree of comfort associated with each correct seating posture varies from individual to individual, and this is related to the variation in the musculo-skeletal characteristics of individuals. Thus, in the prior art orthopedic seat designs, in which a fixed relationship between the seat and backrest portions exists because of a rigidly hinged or jointed arrangement, the degree of comfort required for the correct seating posture of given individuals cannot be entirely matched across the range of variations.
Therefore, it would be desirable to provide an orthopedic seat and backrest combination which is adjustable in accordance with the comfort requirements associated with correct seating postures.